phase 4 report - DNV

RN02: DESIGN OF FLOATING STRUCTURES IN ICE // PART 4 ANNEX AInitiatingeventIce featurenot detectedIce feature driftsinto structureUnable to deflectice structureUnable toescapeOutcomeFrequency(per year)TrueTrueImpact F 1Occurence ofinitiating eventFalseTrueTrueNo impact F 2Impact F 3TrueFalseFalseFalseFalseNo impact F 4No impact F 5No impact F 6Figure A.17-N - Illustration of an event tree for iceberg-structure collision. Modified from Eik and Gudmestad (2010).A.17.2.3 Characterization of ice management performanceVarious analytic methods have been, and can be, developed to characterize the performance of anyicemanagement system across a range of ice scenarios. However, the actual full-scale field experience thatisavailable to calibrate and verify these methods remains quite limited, particularly for high ice class vessels ofnovel design in very severe ice conditions.In this regard, it is important to note that systematic documentation of actual experience is highly recommendedto improve future ice management activities. Full-scale demonstration projects can be beneficial, particularlywhen uncertainties about the effectiveness of ice management systems are both high and very consequential.Given the current state-of-the-art and a general absence of well documented and quantitative information aboutice management effectiveness (particularly for sea ice), it is also recommended that experienced ice managementpersonnel be used to provide judgments on probable ice management effectiveness for the types of quantitativeassessments recommended by this International Standard. In this regard, even undocumented input fromwell experienced operational people is a key factor to recognize, and should be solicited as a key input to anyevaluations about ice management approaches and their effectiveness, at least to the extent possible.Where ice management is used for reducing the applied ice actions on an offshore installation, the followingtypically apply:a) The expected performance of ice detection, tracking and forecasting capabilities and the associateduncertainties are documented so the actual performance of the types of systems or devices used in theice management is reflected.b) The overall performance of ice detection and management systems can be characterized in terms oftheir ability to reduce or alter the frequency and nature of adverse ice events, and reflect the influenceof the other ice and physical environmental factors that are associated with these events. Parametersinfluencing this performance can include:––ice feature dimensions and drift speed,––ice feature mechanical properties,––ice pressure occurrences, pack ice presence around icebergs,––metocean conditions (e.g. poor visibility, sea state).102RUSSIAN–NORWEGIAN COOPERATION PROJECT